Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

167
FXUS63 KLOT 081807
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
107 PM CDT Wed Jul 8 2026

.KEY MESSAGES...

- Dry and warm today with highs in the mid-upper 80s.

- A corridor of heavy rainfall may occur somewhere in the region
  Thursday PM, though confidence in local impacts remains low.
  The strongest storms may be capable of gusty to locally
  damaging wind gusts, mainly south of I-80.

- Mainly dry, warmer weather expected this weekend through early
  next week.

&&

.DISCUSSION...
Issued at 342 AM CDT Wed Jul 8 2026

Winds are light and variable to calm early this morning amidst
an expansive area of surface high pressure. Radiational cooling
under clear skies may lead to patchy fog development, mainly
southeast of a Pontiac, IL to Valparaiso, IN line where
dewpoints depressions are lowest. Can`t fully rule out very
shallow and locally dense fog over low-lying open areas and
fields. Any fog that does develop will quickly erode after
daybreak.

The mid-upper ridge axis will gradually shift east today
allowing a return of southwesterly low-level flow to the area,
which paired with mostly sunny skies will lead to a seasonably
warm day with highs in the mid-upper 80s (upper 70s to lower 80s
possible along the Lake County, IL lakeshore where winds lean
southeast in the afternoon).

To our northwest a shortwave and associated trailing cold front
will lead to thunderstorm development across IA/MN/WI this
afternoon and evening. This activity may attempt to drift into
northwest Illinois very late tonight, likely in a decaying
phase. Nevertheless, can`t fully rule out gusty outflow winds
and a few lightning strikes northwest of a Dixon to Waukegan, IL
line after midnight.

Looking ahead to Thursday through early Friday morning, the
surface front and/or residual outflow boundary may stall over
the area during the day. While there has been an overall
southward trend in model guidance over the past 24 hours with
respect to where the corridor of heaviest rainfall is most
favored, there remains notable model spread in where this
boundary ends up as well as the strength and position of a
separate convectively augmented wave (and associated MCV) from
the Central Plains that is expected to move across the region.
Even with a southerly shift in its track, continue to have
concerns that localized areas or even a narrow corridor of heavy
rainfall may materialize within the vicinity of the
aforementioned stalled boundary on the north side of the system
(hinted at in the 6Z HRRR/NAMNest). Given the local
susceptibility to flooding from recent heavy rains, will need to
continue monitoring model and observational trends closely. The
strongest storms will be capable of precip loaded gusty to
locally damaging wind gusts, though the better potential for
severe weather exists just south of the area into central and
southern Illinois where the stronger mid-level flow is expected.

The forecast for Friday will be largely dependent on Thursday,
though in general the greatest coverage of showers and storms is
favored south of the area. Have maintained precip chances
(20-40%) south of the Chicago metro to account for any showers
and storms that develop on the northern edge of another wave
expected to move across central and southern Illinois. North to
northeasterly low-level flow will lead to slightly cooler
temperatures, in the lower 80s for inland areas and 70s near
the lakeshore.

While a few diurnally driven showers and storms can`t be ruled
out on Saturday, upper level ridging expands across the central
CONUS over the weekend into early next week which should lead to
mainly dry conditions into the first part of next week with
temperatures in the upper 80s to around 90. Given we will be on
the northeast periphery of the ridge we will have to monitor the
potential for thunderstorm complexes rounding the ridge across
the broader region toward midweek.

Petr

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 107 PM CDT Wed Jul 8 2026

VFR conditions will continue through much, if not all, of the
period amid persistent SW winds averaging up to around 10 knots.
There are a few windows for precipitation on Thursday,
highlighted by TS potential late Thursday afternoon and evening.

First, a line of TS developing from northwest Iowa to northern
Wisconsin this evening is expected to gradually decay with
southeast extent overnight. SHRA may survive into far northern
Illinois after daybreak, so have maintained PROB30 SHRA for RFD.

Next, the residual outflow boundary from the earlier storms
should wash out across the area during the morning, but foster
sporadic SHRA through at least mid afternoon. Have therefore
maintained VCSH during this window, though it is feasible that
the Chicago terminals remain completely dry during the morning
and early afternoon.

Finally, a mid-level wave crossing southern Wisconsin Thursday
afternoon will provide a renewed focus for TS develop over
northern Illinois between the 19 and 02Z (particularly 21-01Z at
ORD/MDW). There remains uncertainty in both coverage and
location (TS may remain just south of the terminals), but any TS
will be slow-moving and produce torrential rainfall. Also, any
initial TS originating from southern Wisconsin could push an
outflow boundary with a N/NE wind shift across ORD/MDW/GYY prior
to or during any TS at the terminals.

Kluber

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Air Quality Alert until midnight CDT tonight for INZ001-INZ002-
     INZ010-INZ011.

LM...None.

&&

$$

Visit us at weather.gov/chicago